1. Field of the Invention
The present invention relates to a fabrication apparatus for fabricating semiconductor devices and the like, and a power supply system in the fabrication plant.
2. Description of the Related Art
A semiconductor fabrication plant for fabricating semiconductor devices has a clean room containing a number of fabrication apparatuses, e.g., various processing apparatuses for fabrication steps such as lithography, testing apparatuses, and transfer apparatuses. The plant also has a power supply system for supplying power for operating these various apparatuses. This power supply system includes an installed power source for transforming commercial electric power supplied from an electric power company outside the plant and supplying the transformed power into the plant.
Normally, to start the operation of a fabrication apparatus, an operator (machine operator) operates a power ON switch to start supplying power to the fabrication apparatus to activate it. To stop the operation, the operator operates a power OFF switch to stop the supply of power from the installed power source to the fabrication apparatus to thereby stop the apparatus.
When the plant is in operation, however, trouble rarely occurs to make it necessary to urgently stop the operation of a fabrication apparatus. As a means for urgently stopping a fabrication apparatus, therefore, an emergency stop switch operable by an operator is usually arranged near the apparatus. When the operator operates this switch, an emergency stop circuit (EMO) operates to shut off power supply from the installed power source to all apparatuses such as a fabrication apparatus, air conditioner, and light source, thereby urgently stopping these apparatuses. However, if power supply to all apparatuses is abruptly shut off, the system may run away from the control when reactivated.
When the plant is in operation, supply of power sometimes stops owing to an unexpected power failure (including an instantaneous power failure) such as the power failure of a commercial power source or failure of a power source in the plant. If this is the case, power supply to the emergency stop circuit also stops, and a fail safe function of the emergency stop circuit sets the same state as when the emergency stop switch is pressed, thereby shutting off power supply from the installed power source.
To restart the operation of an apparatus, it is necessary to wait until an operator turns on the power switch after the installed power source is recovered. That is, even when an apparatus stops due to an instantaneous power failure, the operation of the apparatus cannot be restarted without the operation by an operator. When a large number of fabrication apparatuses are installed in the plant, it takes a long time for the operator to turn on the power sources of all fabrication apparatuses. This interferes with an increase in productivity.